OBSERVATIONS. 6 § 
nitrous acid, in part fpontaneoufly, and 
in part by alkali, was edulcorated, dried, 
and made red hot along with fome fat. 
, It weighed 156 grains, and was totally 
attractable by the magnet. By other 
experiments I have found the propor- 
tion of the calx of iron, made at¬ 
tractable by heating it, to the iron in 
a metallic date to be as 7 to 5. As, 
therefore, thofe 156 grains of phlogifti- 
cated calx of iron are equivalent to 11 i t 
grains in a metallic Hate, the quantity 
of pure cobalt metal free from iron 
obtained from one ounce of this cobalt 
ore, the regulus of which weighed 158! 
grains, mult be 47 grains. 
(d) I obferved in the following expe¬ 
riments a remarkable difference between 
the violet calx of cobalt obtained from 
the regulus, and that from the cobalt 
ore (§ 1. c). A fmall quantity of the 
firft, diffolved in fmoking marine acid, 
gave a beautiful fapphire blue colour 
F I had 
